There is an Android app called IMSI-Catcher Detector[0] that is supposed to help you detect when you're connected to a stingray-type device. I ran it for around a year and it never once picked up on anything. I'm not involved on the project and can't personally say if it will catch anything or not, but it is open source[1].

[0] https://cellularprivacy.github.io/Android-IMSI-Catcher-Detec...

[1] https://github.com/CellularPrivacy/Android-IMSI-Catcher-Dete...